PROJECT SUMMARY Arsenic in drinking water poses a serious health hazard to tens of millions of people, especially in parts of the world where the arsenic concentrations far exceed the 10 ppb guideline value set by the World Health Organization. According to a recent study, approximately 44.1 M people in the conterminous U.S. use water from domestic wells. 2.1 million out of the 44.1 million people, are predicted to be using wells with arsenic concentration >10 ?g/L. A large number of liver, lung, and kidney cancer cases as well as the dermal conditions, such as hyperkeratosis and depigmentation are connected to arsenic ingestion. The most devastating case of chronic arsenic exposure is found in Bangladesh. Since the spatial distribution of arsenic in aquifers of the region is highly variable, the ability to distinguish high and low arsenic wells through rapid and reliable testing in the field is critical. Arsenic is second only to lead as the main inorganic contaminant in the original National Priority List of Superfund sites. It is also one of the toxic materials regulated under the Resource Conservation and Recovery Act (RCRA). Therefore, the need also exists for arsenic monitoring at Superfund sites, RCRA landfills, facilities handling arsenic-containing wastes, and sites. However, a reliable, quantitative and easy to use sensor for determination of arsenic in drinking water especially at low ppb levels is not currently available. Conventional methods for determination of arsenic, such as ICP-MS and ICP-AES, are labor-intensive, time consuming, and expensive, while colorimetric tests are not reliable. Most of the currently available colorimetric test kits also use highly toxic chemicals containing mercury or lead and also produce highly toxic gas arsine during the test. Lynntech proposes to develop a simple, safe and easy-to-use device for rapid determination of arsenic in drinking water. The proposed device utilizes electrochemistry for interference removal and quantitative determination of total inorganic arsenic (arsenate + arsenite). This system will only require the user to inject an aliquot of water into the device and take a reading. Additional merits include: accurate quantification of arsenic over a wide range (ppb-ppm), ease of handling, storage and transportation, long shelf life and a low cost.